1. Field of the Invention
The present invention relates to a magnetic disk drive, and more particularly to a data recording and reproducing apparatus having a read/write circuit capable of setting a parameter necessary for a read/write operation for reproducing data from the disk or recording data to the disk.
2. Description of the Related Art
Conventionally, a magnetic disk drive comprises a read/write circuit for reproducing a read data from read signal read from the disk by a head and converting recording data to be recorded to the disk to a write signal (write current).
The read/write circuit can be largely classified to a data reproducing system including an amplifying circuit, a filter circuit, a read pulse generator, and a data recording system for converting recording data to a write current. In the magnetic disk drive, data is recorded to the disk by a predetermined recording frequency, and a data transfer rate at the time of data reproduction is determined based on the recording frequency. In the read/write circuit, it is required that various types of parameters, which are necessary for the read/write operation, be set to suitable values in order to correctly reproduce data recorded by the predetermined recording frequency.
For example, a low pass filter is used as a filter circuit, and parameters such as a cutoff frequency and quantity of boost (dB) must be set to be suitable values. More specifically, for example, as a filter circuit for the read/write circuit, there is used an integrated circuit such as "Power Programmable Electronic Filter (type: SSI32F8001/8002)" manufactured by Silicon Systems Inc. or "Pulse Detector with Programmable Filter (type: SSI32P3040)." Such a filter circuit has an input terminal for setting parameters such as a cutoff frequency or quantity of boost by an input voltage or an input current. Normally, a micro processor (CPU) of the magnetic disk drive sets such parameters in manufacturing the magnetic disk device.
The suitable values of the parameters of the filter circuit forming the read/write circuit are set in manufacturing the magnetic disk drive. However, in a case that the magnetic disk drive shipped as a product is driven, the parameters of the read/write circuit set in manufacturing the drive are not always set to the suitable values by characteristic variations of each parts in manufacturing the drive. Due to this, a read error, which is beyond an allowable range, is often generated.
Particularly, in the magnetic disk device of constant density recording (CDR) type, since the data transfer rate differs for every zone, the suitable parameter of the read/write circuit must be set for every zone. In the CDR type, a plurality of tracks on the disk are divided into a plurality of zones in a radial direction such that a recording density is set be relatively constant over the entire recording surface of the magnetic disk. In other words, the number of sectors differs for each zone. More specifically, the number of sectors is larger toward the zone of the outer peripheral side, and smaller toward the zone of the inner peripheral side. Due to this, the data transfer rate differs for every zone.
Even in such a CDR system, the suitable parameter for every zone of the read/write circuit is normally set in manufacturing the drive. Therefore, similar to the above case, when the magnetic disk drive shipped as a product is driven, the parameters of the read/write circuit set in manufacturing the device are not always set to the suitable values by characteristic variations of each parts in manufacturing the device.